HTML (Hypertext Markup Language) is a language for structuring and presenting content on the web. It uses tags to annotate text and other content within web pages. Key HTML tags include paragraph tags (<p>), heading tags (<h1> through <h6>), lists (<ul>, <ol>, <li>), links (<a href=””>), and images (<img src=””>). Following the three C's of web design - content, code, and creativity - allows developers to effectively structure and present information on web pages using HTML.